lnwallet: simplify fee calculation in evaluateHTLCView

This commit simplifies how we compute the commitment fee rate based
off of the live updates. Prior to this commit we processed all of
the FeeUpdate paymentDescriptors of both ChannelParty's. Now we only
process the last FeeUpdate of the OpeningParty

go.mod

@@ -35,7 +35,7 @@ require (
 	github.com/lightningnetwork/lightning-onion v1.2.1-0.20240712235311-98bd56499dfb
 	github.com/lightningnetwork/lnd/cert v1.2.2
 	github.com/lightningnetwork/lnd/clock v1.1.1
-	github.com/lightningnetwork/lnd/fn v1.2.1
+	github.com/lightningnetwork/lnd/fn v1.2.2
 	github.com/lightningnetwork/lnd/healthcheck v1.2.5
 	github.com/lightningnetwork/lnd/kvdb v1.4.10
 	github.com/lightningnetwork/lnd/queue v1.1.1